This invention relates generally to electrographic copier apparatus utilizing a plurality of discrete film sheets, and more particularly to a sheet film buffer station for such apparatus.
In copending U.S. patent application Ser. No. 427,238 filed Sept. 29, 1982 in the name of Kindt, an electrophotographic copier is described which utilizes a plurality of discrete sheets of photoconductive film. The film sheets are transported seriatim about a continuous path track assembly into operative relation with electrographic process stations. In the reproduction process, in order, each film sheet is uniformly charged, exposed to a light image of a document to be reproduced to form a charge pattern on such sheet, and developed with pigmented thermoplastic marking particles electrostatically attracted to the charge pattern to form a transferable image corresponding to the document image. The transferable image is then transferred to a receiver member to form the document reproduction and the sheet is cleaned for reuse. An advantage to using the plurality of discrete film sheets, as contrasted to the use of a continuous photoconductive web or drum, is that the rate of movement of the respective film sheets through the process stations can be varied to optimize the operation of each process station on the film sheets.
The path length of the track assembly is desirably long enough to accommodate the total number of film sheets between the last station of the reproduction process and the first station. The reason for having such path length is so that, after completion of a reproduction run, no sheet remains in intimate relation with any process station where damage to that sheet by remaining in such station could occur. Alternatively, the track assembly may include a storage chamber, or buffer station, to hold the film sheets between reproduction runs. The employment of a buffer station has significant advantages over the continuous path track assembly in that it shortens the overall path length of the track assembly. That is, the distance between the last process station and the first station, required to accommodate the total number of film sheets, is reduced. Further, the buffer station can store film sheets for a time sufficient to compensate for any variation in the time it takes for individual sheets to complete their travel through a cycle of the reproduction process. By selectively holding individual sheets in the buffer station for an appropriate length of time, the sheets are prevented from bumping into one another due to a cummulative effect of different travel speeds of respective sheets.
A buffer station for rigid photoconductive film plates is shown in U.S. Pat. No. 3,698,602, issued Oct. 17, 1972, in the name of Gnage. In the buffer station of this patent, the film plates, with integral spacers, are in contact with one another and progress seriatim from an entrance location to an exit location. Accordingly, such station would not be suitable for use with non-rigid film sheets. Such plates must be maintained separated by the spacers to prevent damage to the plate surfaces, such as by rubbing contact between the surfaces of adjacent plates. Moreover the travel path of the plates through such buffer station elongates the total plate travel path (when the distance necessary to travel between entrance and exit location of the buffer station is included). Additionally, such buffer station only allows distribution of the plates from the station into the travel path in the same order in which they are received in the station (first plate in is first plate out).